I have never done this myself but in a little booklet I have Snippy Tips 1, it says to.... Split woody stem ends. Submerge flower for a minute. Tip to let the water run off. Keep covered on a bed of moist cotton in a cool place until ready to arrange. Mist frequently. This little booklet was put out by the Garden Club of Toronto. Don't know if this will be of any help, maybe someone else can add to this.

A......

Or you can pick the flowers and float them in a bowl of water.

Easy. Just smash the stems a bit before you put them in water. I use a hammer.

I do this for all flowers with woody stems.